What is it about?
Studying materials under high pressure is a valuable technique. Percy Bridgman won the 1946 Nobel Prize in Physics for pioneering high pressure apparatus and for the his discoveries using it (which included that high pressure, like boiling water, will cook an egg). Until the invention of the diamond-anvil cell (DAC), high-pressure apparatus was massive, using 100-ton hydraulic presses. DACs use a pair of diamonds with tiny flats that, squeezed together by a ton force, generate pressures of many tons per square inch. Early DACs weighed typically about a kilogramme, too much to be convenient for low-temperature (liquid helium, 2K) science. I designed my cell from the diamonds outwards, keeping components small (aided by Willi Scherrer in our Workshops, who trained as a Swiss watchmaker), and so my cell weighed in at 50 grams. Together with a lightweight drive based on the Bowden cable principle (as in bicycle brake cables), it has been extensively used by other laboratories and is commercially available to this day.
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Why is it important?
As well as enabling much research in many laboratories worldwide, my DAC also inspired others to go smaller and light still! I think the record is a megabar cell weighing about 7 grams by Mikhail Eremets.
Perspectives
I enjoyed this project particularly, as it built upon the skills I'd learnt as a teenager, building a model steam locomotive in the workshops of the Socity of Model and Experimental Engineers, London. And, when I started the project, I attended a seminar on high pressure methods. The speaker said there were only two ways of transmitting the ton force to the diamonds and aligning the diamonds for exact parallelism of the two contacting surfaces (without which the diamonds break immediately). I stopped listening, as I started thinking, and by the end of the seminar, I'd found two more ways, one of which I used in my DAC. Eremets used the other in his still smaller DAC.
Professor David James Dunstan
Queen Mary University of London
Read the Original
This page is a summary of: Miniature cryogenic diamond-anvil high-pressure cell, Review of Scientific Instruments, April 1988, American Institute of Physics,
DOI: 10.1063/1.1139846.
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